#include <stdint.h>
#include <string.h>

// AES S-box
static const uint8_t sbox[256] = {
    0x63, 0x7c, 0x77, 0x7b, 0xf2, 0x6b, 0x6f, 0xc5, 0x30, 0x01, 0x67, 0x2b, 0xfe, 0xd7, 0xab, 0x76,
    0xca, 0x82, 0xc9, 0x7d, 0xFA, 0x59, 0x47, 0xf0, 0xad, 0xd4, 0xa2, 0xaf, 0x9c, 0xa4, 0x72, 0xc0,
    0xb7, 0xfd, 0x93, 0x26, 0x36, 0x3f, 0xf7, 0xcc, 0x34, 0xa5, 0xe5, 0xf1, 0x71, 0xd8, 0x31, 0x15,
    0x04, 0xc7, 0x23, 0xc3, 0x18, 0x96, 0x05, 0x9a, 0x07, 0x12, 0x80, 0xe2, 0xeb, 0x27, 0xb2, 0x75,
    0x09, 0x83, 0x2c, 0x1a, 0x1b, 0x6e, 0x5a, 0xa0, 0x52, 0x3b, 0xd6, 0xb3, 0x29, 0xe3, 0x2f, 0x84,
    0x53, 0xd1, 0x00, 0xed, 0x20, 0xfc, 0xb1, 0x5b, 0x6a, 0xcb, 0xbe, 0x39, 0x4a, 0x4c, 0x58, 0xcf,
    0xd0, 0xef, 0xaa, 0xfb, 0x43, 0x4d, 0x33, 0x85, 0x45, 0xf9, 0x02, 0x7f, 0x50, 0x3c, 0x9f, 0xa8,
    0x51, 0xa3, 0x40, 0x8f, 0x92, 0x9d, 0x38, 0xf5, 0xbc, 0xb6, 0xda, 0x21, 0x10, 0xff, 0xf3, 0xd2,
    0xcd, 0x0c, 0x13, 0xec, 0x5f, 0x97, 0x44, 0x17, 0xc4, 0xa7, 0x7e, 0x3d, 0x64, 0x5d, 0x19, 0x73,
    0x60, 0x81, 0x4f, 0xdc, 0x22, 0x2a, 0x90, 0x88, 0x46, 0xee, 0xb8, 0x14, 0xde, 0x5e, 0x0b, 0xdb,
    0xe0, 0x32, 0x3a, 0x0a, 0x49, 0x06, 0x24, 0x5c, 0xc2, 0xd3, 0xac, 0x62, 0x91, 0x95, 0xe4, 0x79,
    0xe7, 0xc8, 0x37, 0x6d, 0x8d, 0xd5, 0x4e, 0xa9, 0x6c, 0x56, 0xf4, 0xea, 0x65, 0x7a, 0xae, 0x08,
    0xba, 0x78, 0x25, 0x2e, 0x1c, 0xa6, 0xb4, 0xc6, 0xe8, 0xdd, 0x74, 0x1f, 0x4b, 0xbd, 0x8b, 0x8a,
    0x70, 0x3e, 0xb5, 0x66, 0x48, 0x03, 0xf6, 0x0e, 0x61, 0x35, 0x57, 0xb9, 0x86, 0xc1, 0x1d, 0x9e,
    0xe1, 0xf8, 0x98, 0x11, 0x69, 0xd9, 0x8e, 0x94, 0x9b, 0x1e, 0x87, 0xe9, 0xce, 0x55, 0x28, 0xdf,
    0x8c, 0xa1, 0x89, 0x0d, 0xbf, 0xe6, 0x42, 0x68, 0x41, 0x99, 0x2d, 0x0f, 0xb0, 0x54, 0xbb, 0x16
};

// Helper function to perform GF(2^8) multiplication
static uint8_t xtime(uint8_t x) {
    return (x << 1) ^ ((x & 0x80) ? 0x1b : 0x00);
}

static uint8_t gmul(uint8_t a, uint8_t b) {
    uint8_t result = 0;
    while (b) {
        if (b & 1) {
            result ^= a;
        }
        a = xtime(a);
        b >>= 1;
    }
    return result;
}

// AES SubBytes transformation
static void sub_bytes(uint8_t *state) {
    for (int i = 0; i < 16; ++i) {
        state[i] = sbox[state[i]];
    }
}

// AES ShiftRows transformation
static void shift_rows(uint8_t *state) {
    uint8_t temp[16];
    temp[0]  = state[0];
    temp[1]  = state[5];
    temp[2]  = state[10];
    temp[3]  = state[15];
    temp[4]  = state[4];
    temp[5]  = state[9];
    temp[6]  = state[14];
    temp[7]  = state[3];
    temp[8]  = state[8];
    temp[9]  = state[13];
    temp[10] = state[2];
    temp[11] = state[7];
    temp[12] = state[12];
    temp[13] = state[1];
    temp[14] = state[6];
    temp[15] = state[11];
    memcpy(state, temp, 16);
}

// AES MixColumns transformation
static void mix_columns(uint8_t *state) {
    uint8_t temp[16];
    for (int i = 0; i < 4; ++i) {
        temp[i * 4 + 0] = gmul(0x02, state[i * 4 + 0]) ^ gmul(0x03, state[i * 4 + 1]) ^ gmul(0x01, state[i * 4 + 2]) ^ gmul(0x01, state[i * 4 + 3]);
        temp[i * 4 + 1] = gmul(0x01, state[i * 4 + 0]) ^ gmul(0x02, state[i * 4 + 1]) ^ gmul(0x03, state[i * 4 + 2]) ^ gmul(0x01, state[i * 4 + 3]);
        temp[i * 4 + 2] = gmul(0x01, state[i * 4 + 0]) ^ gmul(0x01, state[i * 4 + 1]) ^ gmul(0x02, state[i * 4 + 2]) ^ gmul(0x03, state[i * 4 + 3]);
        temp[i * 4 + 3] = gmul(0x03, state[i * 4 + 0]) ^ gmul(0x01, state[i * 4 + 1]) ^ gmul(0x01, state[i * 4 + 2]) ^ gmul(0x02, state[i * 4 + 3]);
    }
    memcpy(state, temp, 16);
}

// AES AddRoundKey transformation
static void add_round_key(uint8_t *state, const uint8_t *round_key) {
    for (int i = 0; i < 16; ++i) {
        state[i] ^= round_key[i];
    }
}

// AES Round Function
inline void aes_single_round_no_intrinsics(uint8_t *state, const uint8_t *round_key) {
    sub_bytes(state);
    shift_rows(state);
    mix_columns(state);
    add_round_key(state, round_key);
}
